PET/CT is the standard imaging modality for assessing lymphoma tumor burden and evaluating response in routine practice and clinical trials. Over the last few years, several PET/CT-based biomarkers have been developed, with metabolic tumor volume (MTV) being the most studied. High-MTV has been consistently associated with shorter survival in different lymphoma subtypes; however, different segmentation thresholds and cutpoints have been proposed, preventing the inclusion of MTV in the decision-making process. In this chapter, we discuss current data on the use of MTV, total lesion glycolysis, and other PET/CT-biomarkers in lymphoma.